Orodispersible tablet containing compacted sildenafil base

ABSTRACT

The invention relates to a process for the preparation of a pharmaceutical intermediate, comprising the steps of (i) mixing (a-i) sildenafil base, (b-i) wicking agent, (c-i) disintegrant, (d-i) optionally glidant; (ii) compacting the mixture; and (iii) milling the compacted material; and to an intermediate obtainable by that process. In addition, the invention relates to a process for the preparation of an orally dispersible tablet (hereinafter also referred to as an “orodispersible tablet”) comprising the intermediate of the invention, and to orodispersible tablets obtainable by that process.

The invention relates to a process for the preparation of apharmaceutical intermediate, comprising the steps of (i) mixing (a-i)sildenafil base, (b-i) wicking agent, (c-i) disintegrant, (d-i)optionally glidant; (ii) compacting the mixture; and (iii) milling thecompacted material; and to an intermediate obtainable by that process.In addition, the invention relates to a process for the preparation ofan orally dispersible tablet (hereinafter also referred to as an“orodispersible tablet”) comprising the intermediate of the invention,and to orodispersible tablets obtainable by that process.

The IUPAC name of sildenafil [INN] is1-[[3-(1-methyl-7-oxo-3-propyl-6,7-dihydro-1H-pyrazolo-[4,3-d]pyrimidine-5-yl)-4-ethoxyphenyl]-sulphonyl]-4-methylpiperazine. The chemical structure of sildenafil is shown in formula (1)below:

Sildenafil is a potent selective inhibitor of type 5 cGMP-specificphosphodiesterase (PDE-5), which is responsible for the reduction ofcGMP in the Corpus cavernosum. Sildenafil in the form of its citratesalt is marketed under the trade name Viagra® for the treatment oferectile dysfunction.

Various processes for the preparation of an orodispersible tabletcontaining sildenafil are proposed in the state of the art. EP 0 960 621A2 describes the preparation of porous orodispersible tablets containingsildenafil, wherein a water-soluble, meltable binder, at least oneexcipient and sildenafil are first shaped into a tablet, after which thebinder is melted and solidified.

EP 1 120 120 A1 describes a process for the preparation of anorodispersible tablet, which comprises mixing a cyclic GMPphosphodiesterase inhibitor with a saccharide, kneading that mixturewith an organic solvent, water or an aqueous organic solvent and thencompressing it in a mould to form an orodispersible tablet.

WO 2009/123626 describes orally dispersible tablets with PDE-5inhibitors, wherein up to 50% by weight of cation exchange resin isrequired for formulation purposes, which can have a negative effect onthe feeling in the mouth. Furthermore, the sildenafil formulationsdescribed are complex to prepare, since two wet granulation steps areneeded (1. wet granulation: sildenafil+cation exchange resin, 2. wetgranulation: excipients).

The processes described in the state of the art for the preparation oforodispersible tablets are complex and only make it possible to obtainorodispersible tablets with a content of active agent of well under 50%by weight. However, if the dosage remains unchanged, such a low contentof active agent leads to a higher tablet weight, which can often causeproblems with regard to the tablet properties. Orodispersible tabletswith too high a tablet weight (e.g. more than 300 mg) are often rejectedby patients, because after the orodispersible tablet has disintegrated,there is a large amount of tableting mixture in the buccal cavity, whichis felt to be disturbing and unpleasant. The disintegration time and thefeeling caused in the mouth by the tablets obtainable in the state ofthe art are in need of improvement. A drug load of more than 45% or evenmore than 50% cannot be advantageously achieved with the processesdescribed, in particular not with an advantageous disintegration timeand a pleasant feeling in the mouth. In addition, it has been found thatit is not possibly simply to increase the drug load with the processknown in the state of the art, also with regard to the physicalparameters, since reducing the proportion of excipients leads todisadvantageous tablet properties (e.g. in terms of hardness andfriability).

In addition, it has been found that the disintegration time of theorodispersible tablets described in the state of the art increasesundesirably after lengthy storage.

To sum up, it can be stated that the formulations proposed in the stateof the art involve disadvantages. The objective of the invention wastherefore to overcome those disadvantages.

Specifically, it was an object of the present invention to provide anorodispersible tablet containing sildenafil which can have a drug loadof more than 50% by weight.

In addition, it was an object of the invention to provide anorodispersible tablet which, after the patient has taken it, is felt notto be disturbing and not unpleasant in terms of taste and the feeling inthe mouth.

In addition, it was an object of the invention to provide an oral dosageform that achieves a good feeling in the mouth and a good taste for thepatient (i.e. the patient should not experience an unpleasant—e.g.bitter—taste, and the mass of tablet material should not be so great perse that it is felt to be unpleasant).

The expression “feeling in the mouth” as used herein describes thephysical and chemical interactions of a substance or mixture ofsubstances (in the present case especially the orodispersible tablet ofthe invention) in the mouth. It includes the impressions from the firstcontact with the palate, chewing and swallowing and the aftertaste.

The feeling in the mouth can be described on the basis of the followingcriteria, for example (“sample” means a characteristic composition,formulation or pharmaceutical final dosage form containing active agentand excipient or excipients):

-   -   a mouth lining: nature and degree of the coating on teeth and        mucous membrane of the buccal cavity. It is usually relevant to        consider the lining after the sample has been chewed or has        disintegrated, i.e. immediately before swallowing;    -   density: density of the cut surface in the sense of the density        of the packing, i.e. layering or continuous compressed material        or granules or the like comprising or consisting of, for        example, the mixture according to a formulation, after a sample        or, as described, a product or a final dosage form has been        completely severed with the molars;    -   elasticity: ability of the sample (or the product or the final        dosage form) to return to its original shape after being exposed        to a force;    -   hardness: measure of the force subjectively felt to be required        in order to deform the sample by a defined amount, or to break        it;    -   moisture: amount or effect of a given amount of liquid perceived        as such on the surface of the sample;    -   a moisture absorption: amount of saliva absorbed by the sample;    -   uniformity: describes the uniformity of a sample (taste,        texture, colour etc.);    -   granularity: degree of graininess felt during the chewing        process;    -   adhesion: the force required to remove the material to be tested        from a particular surface (lips, teeth, palate etc.);    -   roughness: degree of sensed abraded matter left behind on the        tongue by the sample;    -   smoothness: degree to which the sample slides over the tongue;    -   heaviness: weight of the sample sensed upon its first contact        with the tongue;    -   crushability: the force required to make the sample        disintegrate.

In addition, it was an object of the invention to provide anorodispersible tablet that exhibits rapid disintegration in the mouthand even after lengthy storage still satisfies the requirements of rapiddisintegration and not only possesses the general requirements expectedof pharmaceutical products, such as the stability of the active agent,but also avoids any discoloration or decomposition or other undesirablechanges of a physical, chemical or physico-chemical nature.

“Rapid disintegration” in the context of this invention means adisintegration time, determined in accordance with Ph. Eur. 6.0, section2.9.1 Test A, of less than 100 seconds, preferably less than 50 seconds,even more preferably less than 30 seconds, in particular less than 25seconds.

In addition, the intention is to provide orodispersible tablets whichexhibit both advantageous friability and advantageous hardness.

It was possible to solve the problems by means of a process for thepreparation of an orodispersible tablet containing sildenafil base,wicking agent and disintegrant, especially by employing a compactingstep.

The subject matter of the invention is therefore a process for thepreparation of a pharmaceutical intermediate, comprising the steps of

-   (i) mixing    -   (a-i) sildenafil base,    -   (b-i) wicking agent,    -   (c-i) disintegrant,    -   (d-i) optionally glidant;-   (ii) compacting the mixture; and-   (iii) milling the compacted material.

A further subject matter of the invention is a process for thepreparation of an orodispersible tablet containing sildenafil base,comprising the steps of

-   (I) preparing the intermediate of the invention,-   (II) mixing the intermediate with further pharmaceutical excipients,    and-   (III) compressing the mixture from step (II) into an orodispersible    tablet.

The processes for the preparation of the intermediate of the inventionand the orodispersible tablet of the invention can thus be combined. Theinvention therefore also relates to a process for the preparation of anorodispersible tablet containing sildenafil base, comprising the stepsof

-   (I) preparing an intermediate, comprising the steps of    -   (i) mixing        -   (a-i) sildenafil base,        -   (b-i) wicking agent,        -   (c-i) disintegrant,        -   (d-i) optionally glidant,    -   (ii) compacting the mixture, and    -   (iii) milling the compacted material,-   (II) mixing the intermediate with further pharmaceutical excipients,    and-   (III) compressing the mixture from step (II) into an orodispersible    tablet.

In addition, a subject matter of the invention is an intermediateobtainable by the process of the invention and an orodispersible tabletobtainable by the process of the invention.

A further subject matter of the invention is an orodispersible tabletcontaining

-   45 to 70% by weight sildenafil base,-   10 to 35% by weight wicking agent, in particular microcrystalline    cellulose,-   5 to 20% by weight disintegrant, in particular crospovidone,-   0 to 5% by weight glidant, in particular silicon dioxide,-   0 to 10% by weight lubricant, in particular sodium stearyl fumarate    or magnesium stearate.

Finally, a subject matter of the invention is the use of sildenafil basein particulate form, wherein the D50 value of the particle sizedistribution is 10 to 55 μm, preferably 20 to 45 μm, and the D90 valueof the particle size distribution is 60 to 250 μm, preferably 100 to 200μm, for the preparation of an orodispersible tablet, preferably for thepreparation of an orodispersible tablet with a hardness of 30 to 90 Nand a friability of less than 1%, preferably 0.01 to 0.5%. In analternative preferred embodiment, a subject matter of the invention isthe use of sildenafil base in particulate form, wherein the D50 value ofthe particle size distribution is 1 to 25 μm, preferably 2 to 15 μm, andthe D90 value of the particle size distribution is 5 to 80 μm,preferably 10 to 55 μm, for the preparation of an orodispersible tablet,preferably for the preparation of an orodispersible tablet with ahardness of 30 to 90 N and a friability of less than 1%, preferably 0.01to 0.5%.

The particle size distribution is preferably determined, as explained inmore detail below, with a laser diffraction measuring unit, which isknown per se and is applied to perform a dry measurement. The detailsregarding D10, D50 and D90 etc. relate here to the total throughputcurve, weighted with a calculated representative diameter or volume ofthe particles; hence, D10 is the particle size at which 10% are smallerthan the D value stated, D50 means 50% are smaller, and D90 that 90% aresmaller than the D value stated.

As explained above, the present invention relates to a process for thepreparation of a pharmaceutical intermediate.

According to the present invention, an “intermediate” is usuallyunderstood to mean a pharmaceutical composition which is notadministered directly, but is instead converted into an applicable oraldosage form by means of suitable processes, such as granulation and/orcompression.

The process of the invention for the preparation of the pharmaceuticalintermediate comprises the steps of (i) mixing, (ii) compacting themixture and (iii) milling the compacted material.

“Mixing” is understood in the context of the invention as meaning aprocess for combining substances with the aim of achieving asubstantially homogeneous distribution of different substances by theaction of mechanical forces. Mixing for the purposes of the invention isperformed in conventional mixing devices, such as asymmetric movedmixers, roll mixers, shaking mixers, free-fall mixers, shear mixers,ploughshare mixers, planetary mixing kneaders, Z or sigma kneaders orfluid or intensive mixers. It is preferable to use an asymmetric movedmixer.

The mixing time in step (i) is usually 1 to 30 minutes, preferably 2minutes to 20 minutes, more preferably 5 minutes to 17 minutes.

As already mentioned, step (i) of the process of the invention comprisesmixing the components (a-i) sildenafil base, (b-i) wicking agent, (c-i)disintegrant, (d-i) optionally glidant and optionally furtherpharmaceutical excipients.

Especially in the preparation of larger batches, it has provenadvantageous if, in the preparation of the intermediate of theinvention, the wicking agent (b-i) and the glidant (d-i) are premixed.Hence, it is preferable that in step (i), a premixed mixture of wickingagent and glidant is used. Similarly, in the premixing step described,sweeteners and/or flavourings can be premixed as well. It isparticularly preferable for the premixing to be performed by premixingfor 5 to 30 minutes. By premixing the wicking agent and glidant, it wasin particular possible to exert a positive influence on the uniformityof the content.

In the context of this invention, component (a-i) sildenafil base isunderstood to mean1-[[3-(1-methyl-7-oxo-3-propyl-6,7-dihydro-1H-pyrazolo-[4,3-d]pyrimidine-5-yl)-4-ethoxyphenyl]-sulphonyl]-4-methylpiperazine in accordance with formula (1) above. The compound of formula(1) is present here in the form of the free base and not in salt form.

Component (a-i) sildenafil base is usually employed in step (i) in anamount of 40 to 98% by weight, preferably 55 to 95% by weight, inparticular 60 to 90% by weight, based on the total weight of theintermediate.

In general, component (b-i) wicking agent is a substance with theability to draw up a biological fluid (preferably water) into a solid(preferably in the orodispersible tablet of the invention or in theintermediate of the invention, preferably by means of physisorption).Physisorption is defined as a form of adsorption in which the liquidmolecules can adhere to the surface of the wicking agent, preferably bymeans of van der Waals binding between the surface of the wicking agentand the adsorbed fluid molecule (preferably water). Normally a wickingagent achieves this with or without swelling. Normally, a non-swellingwicking agent which attracts water will ultimately have a volumeconsisting substantially of the volume of the wicking agent and theamount of water which it attracts. In general, a swelling wicking agentwill have a volume consisting substantially of the volume of the wickingagent, the volume of the water which it attracts, and an additionalvolume, caused by steric and molecular forces acting between thecellulose chains and water molecules deposited on them. It is preferableto use non-swelling wicking agents or wicking agents whose swellingbehaviour in relation to the water transport behaviour is of minorimportance for the effect of the invention described in the following.

In the intermediate of the invention or in the tablet of the invention,the wicking agent (b-i) preferably causes the formation of channels orpores. This facilitates the penetration of the water molecules into theorodispersible tablet, especially by physisorption. The function of thewicking agent therefore consists in transporting water to the surfacesinside the intermediates in order in this way to create channels in or anetwork on an enlarged surface.

Examples of wicking agents used are: microcrystalline cellulose,silicified microcrystalline cellulose, kaolin, titanium dioxide, fumedsilica, aluminium, niacinamide, M-pyrol, bentonite, magnesium-aluminiumsilicate, polyester, polyethylene, or mixtures thereof. The wickingagents of the pharmaceutical composition of the present inventionpreferably contain cellulose and cellulose derivatives, such assilicified microcrystalline cellulose, and mixtures thereof.Microcrystalline cellulose is particularly preferably used as a wickingagent. It is commercially available, under the trade name Avicel® forexample. In the context of this invention, microcrystalline cellulosewith a weight-average molecular weight of 10,000 to 70,000 g/mol,preferably 25,000 to 45,000 g/mol, more preferably 30,000 to 40,000g/mol is usually employed. The weight-average molecular weight isusually determined by means of gel permeation chromatography in thiscontext.

It is preferable here that a microcrystalline cellulose is usuallyemployed which is prepared from native alpha-cellulose by complete orpreferably partial acid hydrolysis. In the context of this invention,microcrystalline cellulose with a water content of <1.5% by weight,preferably 0.01 to 1.2% by weight, is usually employed. In the contextof this application, the water content is preferably determined with aMettler Toledo HR83 halogen moisture apparatus at 80° C. and 6 min.measuring time. Usually, a sample weighing 3.0 g is analysed.

Component (b-i) wicking agent is usually employed in step (i) in anamount of 1 to 40% by weight, more preferably 5 to 35% by weight, inparticular 10 to 30% by weight, based on the total weight of theorodispersible tablet.

Component (c-i) disintegrant is the term generally used for one or moresubstances which accelerate the disintegration of a dosage form,especially a tablet, after it is placed in water. Suitable disintegrantsare, for example, organic disintegrants such as carrageenan, cellulosesand cellulose derivatives, croscarmellose, starches and starchderivatives, sodium carboxymethyl starch, polysaccharides, soyapolysaccharides, alginates and crospovidone. Alkaline disintegrants canlikewise be used. The term “alkaline disintegrants” means disintegrantswhich, when dissolved in water, produce a pH level of more than 7.0.Mixtures of the above-mentioned disintegrants may also be used.

Crospovidone is preferably used as the disintegrant. In the context ofthis invention, crospovidone is usually understood to mean across-linked homopolymer of N-vinyl-2-pyrrolidone, which is alsoreferred to as cross-linked polyvinyl polypyrrolidone (PVPP).Crospovidone can generally be prepared in accordance with U.S. Pat. No.2,938,017 and usually has a weight-average molecular weight of more than1,000,000 g/mol.

Component (c-i) disintegrant is usually employed in step (i) in anamount of 1 to 30% by weight, more preferably 2 to 15% by weight,especially 5 to 12% by weight, based on the total weight of theorodispersible tablet.

In principle, it would also be possible to use a copolymer obtainable bythe copolymerisation of methacrylic acid and divinyl benzene asdisintegrant (c-i). A copolymer of this kind is known under the name ofpolacrilin, especially in the form of the potassium salt (polacrilinpotassium, especially as monographed in accordance with the USPharmacopoeia).

Polacrilin potassium can be illustrated by the following structuralformula.

where x and y are natural numbers, such as 10¹ to 10²⁰, preferably 10⁶to 10¹⁸. The ratio of x to y is usually 50:1 to 1:1, preferably 20:1 to2:1, particularly preferably 10:1 to 3:1.

The use of polacrilin potassium (e.g. in amounts of 50% by weight) may,however, have a negative effect on the feeling in the mouth. In apreferred embodiment, the orodispersible tablet of the inventiontherefore contains less than 10% by weight polacrilin potassium,particularly preferably less than 5% by weight polacrilin potassium, inparticular no (i.e. 0% by weight) polacrilin potassium.

Component (d-i) glidant usually means substances which serve to improvepowder flowability. The task of glidants is to reduce both theinterparticular friction (cohesion) between the individual particles ina tableting mixture and their adherence to the wall surfaces of thepress mould (adhesion). One example of an additive to improve powderflowability is disperse silicon dioxide (e.g. obtainable as Aerosil®).Preferably, silicon dioxide is used with a specific surface area of 50to 400 m²/g, determined by gas adsorption in accordance with Ph. Eur.,6th edition 2.9.26.

Component (d-i) glidant is usually employed in step (i) in an amount of0 to 10% by weight, more preferably 0.1 to 5% by weight, especially 0.5to 3% by weight, based on the total weight of the intermediate.

In addition, in a preferred embodiment, the sweeteners and/orflavourings explained in more detail below may be added in step (i).

It has unexpectedly been found that in order to solve the problemsdescribed at the beginning, it is particularly advantageous if in step(i) of the process of the invention the substances used are present witha specific particle size distribution. Especially with regard to thefeeling in the mouth and the physical characteristics of a resultingorodispersible tablet, the particle size distribution can be important,it being necessary to take into account both the D50 value (inparticular for the feeling in the mouth) and also the D90 value (inparticular for physical characteristics such as hardness andfriability).

In a preferred embodiment, particulate sildenafil base is therefore usedas component (a-i) in which the D50 value of the particle sizedistribution of the particulate sildenafil base is 1 to 25 μm, morepreferably 2 to 15 μm. The D90 value of the particle size distributionof the particulate sildenafil base is preferably 5 to 80 μm, morepreferably 10 to 55 μm. The D10 value of the particle size distributionof the particulate sildenafil base is preferably 0.1 to 5 μm, morepreferably 1.0 to 4.0 μm.

In a further preferred embodiment (both in the preparation of theintermediate of the invention and in the preparation of theorodispersible tablet of the invention), the wicking agent (b) and/orthe disintegrant (c) are used in particulate form, in which the D50value of the particle size distribution is 20 to 120 μm, more preferably50 to 110 μm. The D90 value of the particle size distribution of thewicking agent and/or disintegrant is preferably 100 to 300 μm, morepreferably 125 to 250 μm.

In a further preferred embodiment, the ratio between the D90 value andD50 value (=D90/D50) of sildenafil base, wicking agent and/ordisintegrant has a value of between 1.1 and 25, preferably between 2.0and 8.0, particularly preferably between 2.5 and 6.0.

In a further preferred embodiment, the ratio between the D50 value andD10 value (=D50/D 10) of sildenafil base, wicking agent and/ordisintegrant has a value of between 2 and 550, preferably between 5 and45, particularly preferably between 8 and 12.

In a further preferred embodiment, the ratio between the D90 value andD10 value (=D90/D10) of sildenafil base, wicking agent and/ordisintegrant has a value of between 12 and 2,500, preferably between 25and 200, particularly preferably between 40 and 60.

The “particle size” is determined in the context of this invention bymeans of laser diffractometry. In particular, a Malvern InstrumentsMastersizer 2000 is used to determine the diameter (dry measurement at20° C., dispersed in air), the evaluation being performed according tothe Fraunhofer model). The average particle diameter (=the averageparticle size), which is also referred to as the D50 value of theintegral volume distribution, is defined in the context of thisinvention as the particle diameter at which 50% by volume of theparticles have a smaller diameter than the diameter which corresponds tothe D50 value. Similarly, 50% by volume of the particles then have alarger diameter than the D50 value. The D90 value of the particle sizedistribution is accordingly defined as the particle size at which 90% byvolume of the particles have a smaller particle size than the particlesize corresponding to the D90 value. Analogously, the D10 value of theparticle size distribution of the intermediate is defined as theparticle size at which 10% by volume of the particles have a smallerparticle size than the particle size corresponding to the D 10 value.

In a further preferred embodiment of the process of the invention, theratio of the weight of component (a-i) to the combined weight ofcomponents (b-i) and (c-i) is 7:1 to 1:3, preferably 4:1 to 1:2,particularly preferably 3:1 to 1:1.

In addition, in a further preferred embodiment of the process of theinvention, the ratio of the weight of components (b-i) to (c-i) is 15:1to 1:2, preferably 10:1 to 1:1, particularly preferably 7:1 to 3:1.

The mixture obtained from step (i) preferably has a water content of0.01 to 4% by weight, preferably 0.1 to 2% by weight, in particular 0.2to 1.5% by weight. The water content here is determined by means of theabove-mentioned halogen moisture method.

In step (ii), the mixture obtained from step (i) is compacted. In thecontext of this invention, compacting is usually understood to mean theconversion of a powder mixture by applying pressure, preferablymechanical pressure, into compacted material, such as slugs orbriquettes.

The compacting can be performed in conventional compacting apparatuses.The compacting is preferably carried out in a roll compacter, e.g.Polygran® (Gerteis). The rolling force is usually 1 to 50 kN/cm,preferably 2 to 30 kN/cm, more preferably 3 to 15 kN/cm. The gap widthof the roll granulator is, for example, 0.8 to 6 mm, preferably 1.5 to5.0 mm, more preferably 2.5 to 4.0 mm, especially 2.8 to 3.8 mm.

The compacting conditions are usually selected such that theintermediate of the invention is present in the form of a slug ofcompacted material, the density of the intermediate being 0.8 to 1.3g/cm³, preferably 0.85 to 1.20 g/cm³, especially 0.90 to 1.15 g/cm³. Thefigures relate to the apparent density.

In step (iii), the compacted material obtained in step (ii) is milledinto granules. The milling in this context can usually be carried outwith the aid of milling tools, such as counter-rotating toothed-rollcrushers, sieves or mixers as described above. It is preferable to usesieves for this purpose, especially sieves with a mesh width of 0.1 to 5mm, preferably 0.5 to 3 mm, more preferably 0.75 to 2 mm, especially 0.8to 1.8 mm. Alternatively, mixers can also be used, such as asymmetricmoved mixers.

In a preferred embodiment, the milling conditions are selected such thatthe resulting particles (granules) have a particle size (D50) of 50 to400 μm, more preferably 60 to 250 μm, even more preferably 90 to 200 μm,especially 110 to 180 μm.

The resulting intermediates can then be used for the preparation of anorodispersible tablet of the invention. As explained above, the presentinvention also relates in addition to a process for the preparation ofan orodispersible tablet containing sildenafil base, comprising thesteps of

-   (I) preparing an intermediate of the invention,-   (II) mixing the intermediate with further pharmaceutical excipients,    and-   (III) compressing the mixture from step (II) into an orodispersible    tablet.

The term “orodispersible tablet” is understood in the context of thisinvention to mean an orally dispersible tablet. Hence, an orodispersibletablet is a tablet that disintegrates orally, in the buccal cavity.During or after disintegration, the components of the tablet of theinvention may not be dissolved at all, or may be partially or completelydissolved by saliva. The orodispersible tablet is usually an uncoatedtablet, i.e. it is not coated or film-coated. In particular, theorodispersible tablet is not a tablet coated with a polymer that isinsoluble in saliva, as is described in U.S. Pat. No. 6,221,402 B1.

According to Ph. Eur. 6.0, orodispersible tablets must disintegratewithin 3 minutes. In the context of this invention, it is preferablethat the orodispersible tablets of the invention should have adisintegration time of less than 100 seconds, more preferably less than50 seconds, particularly preferably less than 30 seconds, in particularless than 25 seconds, in the mouth.

The disintegration time is determined in accordance with Ph. Eur. 6.0,section 2.9.1 Test A. Water is preferably used as the test liquid. Whenin the context of this application reference is made to the averagedisintegration time, this means the average of the disintegration timesdetermined for 6 tablets.

The orodispersible tablets of the invention usually contain sildenafilbase in a mass of 15 to 250 mg, more preferably 20 to 150 mg. Inparticular, they contain 25 mg, 50 mg or 100 mg of sildenafil base.

The orodispersible tablets of the invention usually have a total weightof less than 500 mg, more preferably less than 350 mg, in particularless than 250 mg. The orodispersible tablets of the invention usuallyhave a weight of 35 mg, preferably 50 mg or more, in particular morethan 60 mg.

In a preferred embodiment, the orodispersible tablets of the inventionhave a proportion of sildenafil base of 45 to 70% by weight, preferably50 to 65% by weight, more preferably 51 to 60% by weight, based on thetotal weight of the orodispersible tablet.

With a content of active agent of 20 to 30 mg, the orodispersibletablets of the invention usually have a total weight of less than 200mg, more preferably less than 150 mg, in particular less than 100 mg.When the content of active agent is 20 to 30 mg, the orodispersibletablets of the invention usually have a weight of more than 35 mg,preferably 50 mg or more, in particular more than 60 mg.

With a content of active agent of more than 30 mg and less than 70 mg,the orodispersible tablets of the invention usually have a total weightof less than 300 mg, more preferably less than 150 mg, in particularless than 120 mg. The orodispersible tablets of the invention usuallyhave a weight of more than 60 mg, preferably 80 mg or more, inparticular more than 85 mg.

With a content of active agent of 70 mg to 150 mg, the orodispersibletablets of the invention usually have a total weight of less than 500mg, more preferably less than 350 mg, in particular less than 300 mg.

The weight ratio of active agent to excipients in the orodispersibletablets of the invention is usually 5:1 to 1:3, preferably 3:1 to 1:2,especially 2.0:1 to 1:1.5.

The orodispersible tablets of the invention are therefore clearlydistinct from “chewable tablets”, since the latter usually have a higherweight (approx. 1.5 to 3 g) and a longer disintegration time.

The orodispersible tablets of the invention usually have a hardness 25to 120 N, preferably 30 to 90 N, more preferably 35 to 60 N. Thehardness is usually determined in accordance with Ph. Eur. 6.0, section2.9.8. When in the context of this application reference is made to theaverage hardness, this means the average of the hardness determined for10 tablets.

In addition, the resulting tablets preferably have a friability of lessthan 3%, particularly preferably less than 1%, especially less than0.5%. The friability is determined in an apparatus in accordance withPh. Eur. 6.0, section 2.9.7, where 20 tablets are tested for 10 minutesat 25 r.p.m. and 25° C.

In a preferred embodiment, the orodispersible tablets of the inventionpreferably have a water content of <4.5% by weight, preferably 0.01 to3.0% by weight, in particular 0.1 to 1.5% by weight, determined with theHR83 halogen moisture apparatus explained above.

In step (I) of the process of the invention for the preparation of anorodispersible tablet, the intermediate of the invention is prepared asdescribed above. The intermediate of the invention then forms the “innerphase” in the process of the invention for the preparation of theorodispersible tablet. The components of the inner phase are alsoreferred to as “intragranular components”.

In step (II) of the process of the invention for the preparation of anorodispersible tablet, the intermediate of the invention is mixed withfurther pharmaceutical excipients. In the process of the invention forthe preparation of the orodispersible tablet, the excipients added instep (II) then form the “outer phase”. The components of the outer phaseare also referred to as “extragranular components”.

Further pharmaceutical excipients in this context can usually be anystandard pharmaceutical excipients for the preparation of a tablet,especially an orodispersible tablet.

The term “mixing” is understood here in the context of the invention asdefined above.

In a preferred embodiment, the pharmaceutical excipients used in step(II) are the components (b-ii) wicking agent, (c-ii) disintegrant,optionally (d-ii) glidant and optionally (e-ii) lubricant. Thedesignations (b-ii), (c-ii), (d-ii) and (e-ii) indicate that theseexcipients are added to form the outer phase.

In this context, the components wicking agent (b-ii), disintegrant(c-ii) and glidant (d-ii) are understood as defined above for thepreparation of the intermediate of the invention.

Lubricants (e-ii) are generally substances which are used in order toreduce sliding friction. In particular, the intention is to reduce thesliding friction found during tablet pressing between the punches movingup and down in the die and the die wall, on the one hand, and betweenthe edge of the tablet and the die wall, on the other hand. Suitablelubricants are, for example, stearic acid, adipic acid, sodium stearylfumarate (e.g. Pruv®), magnesium stearate and/or calcium stearate.Stearyl fumarate (e.g. PRUV®) is preferably used as a lubricant in thecontext of the invention sodium. Magnesium stearate is particularlypreferably used as a lubricant, especially with batch sizes of more than5 kg.

Component (b-ii) wicking agent is usually employed in step (II) in anamount of 1 to 10% by weight, more preferably 2 to 8% by weight, inparticular 3 to 7% by weight, based on the total weight of theorodispersible tablet.

Component (c-ii) disintegrant is usually employed in step (II) in anamount of 1 to 10% by weight, more preferably 2 to 8% by weight, inparticular 3 to 6% by weight, based on the total weight of theorodispersible tablet.

Component (d-ii) glidant is usually employed in step (II) in an amountof 0 to 10% by weight, more preferably 0.1 to 5% by weight, inparticular 0.5 to 3% by weight, based on the total weight of theorodispersible tablet.

Component (e-ii) lubricant is usually employed in step (II) in an amountof 0 to 10% by weight, more preferably 0.1 to 7% by weight, inparticular 0.5 to 5% by weight, based on the total weight of theorodispersible tablet.

In the process of the invention, the weight ratio of intragranularwicking agent (b-i) to extragranular wicking agent (b-ii) is usuallyfrom 10:1 to 1:1, preferably 5:1 to 2:1. In addition, the weight ratioof intragranular disintegrant (c-i) to extragranular disintegrant (c-ii)is usually from 5:1 to 1:5, preferably 2:1 to 1:2. Furthermore, theweight ratio of intragranular glidant (d-i) to extragranular glidant(d-ii) is usually from 5:1 to 1:5, preferably 2:1 to 1:2.

In a preferred embodiment of the process of the invention for thepreparation of the intermediate or in the process of the invention forthe preparation the orodispersible tablet, microcrystalline cellulose isused as the wicking agent (b-i) and/or (b-ii), and/or crospovidone isused as the disintegrant (c-i) and/or (c-ii).

Anti-stick agents may optionally be used as further pharmaceuticalexcipients. “Anti-stick agents” are usually understood to meansubstances which reduce agglomeration in the core bed. Examples aretalcum, silica gel, polyethylene glycol (preferably with 2,000 to 10,000g/mol weight-average molecular weight) and/or glycerol monostearate.Talcum is preferably used. Anti-stick agents are usually employed in anamount of 0 to 5% by weight, preferably 0.1 to 2% by weight, based onthe total weight of the orodispersible tablet.

Fillers can likewise be used as further pharmaceutical excipients.Fillers are, for example, calcium phosphates such as calcium hydrogenorthophosphate, especially in the form of the dihydrate, calciumcarbonate, magnesium carbonate, magnesium oxide, and/or calciumsulphate. The orodispersible tablet of the invention may contain fillersin the inner and/or outer phase.

Furthermore, sweeteners and/or flavourings can be used as furtherexcipients. Sweeteners and/or flavourings may be contained both in theinner and in the outer phase.

It is preferable to use sweeteners which have a sweetening power of 0.2to 13,000, preferably >1 to 4,000, in particular 10 to 1,000, based onthe sweetening power of cane sugar (=1.0).

Examples are milk sugar (0.27-0.3), glycerine (0.5-0.8), D-glucose(0.5-0.6), maltose (0.6), galactose (0.6), invert sugar (0.8-0.9), canesugar (1.0), xylitol (1.0), D-fructose (1.0-1.5), sodium cyclamate (30),D-tryptophan (35), chloroform (40), glycyrrhizin (50), acesulphame(130), aspartame (180-200), dulcin (200), Suosan® (350), saccharine(sodium salt) (400-500), saccharine (ammonium salt) (600),1-bromo-5-nitroaniline (700), naringine dihydrochalcone (1,000-1,500),thaumatin, monellin (peptides) (3,000), P-4000,n-propoxyp-2-amino-4-nitrobenzene (4,000), alitame (3,000) and/orneotame (13,000). The numerical value in brackets shows the sweeteningpower based on crude sugar. Thaumatin and/or neohesperidin DC canlikewise be used.

In the orodispersible tablet of the invention, sweeteners are usuallyemployed in an amount of 0.1 to 5% by weight, more preferably 0.5 to 4%by weight, in particular 0.1 to 3% by weight, based on the total weightof the orodispersible tablet.

The orodispersible tablets of the invention may also contain one or moreflavourings. In the context of this application, the term “flavourings”is to be understood as defined in Council Directive 88/388/EEC of 22Jun. 1988.

In step (III) of the process of the invention, the mixture obtained fromstep (II) is compressed into an orodispersible tablet. “Compressing”here is usually understood to mean converting a mixture of substancesinto a dosage form, preferably an orodispersible tablet, with the aid ofa tableting machine by applying pressure.

For the compressing step (III), substantially the intermediate of theinvention in granulated form with further pharmaceutical excipients asdescribed below is used.

The tableting conditions are preferably selected such that the resultingtablets have a ratio of tablet height to weight of 0.01 to 0.1 mm/mg,particularly preferably 0.03 to 0.06 mm/mg.

Conventional tableting machines used in the production of tablets can beused. Rotary presses or eccentric presses are preferably used. Byapplying a suitable compaction force, the problems explained at thebeginning can be solved particularly advantageously, especially withregard to the physical properties (e.g. hardness and friability) of thetablets to be prepared. In the case of rotary tableting presses, acompressive force of 0.003 to 0.40 kN/mm, preferably 0.006 to 0.1 kN/mm,is usually applied. The compressive force is applied here as a force inkilonewtons per mm² tablet surface area, preferably the perpendicularlyprojected tablet surface area.

In the case of eccentric tableting presses, a compressive force of 0.01to 0.07 kN/mm with a Korsch® EK0 or Korsch® XP1 is usually applied.

In a preferred embodiment, the process of the invention for thepreparation of the intermediate and the process of the invention for thepreparation of the orodispersible tablet is carried out in the absenceof solvents. Solvents in this context usually mean water and/or organicsolvents, such as methanol, ethanol and isopropanol, for example.

As already explained, the present invention relates to an intermediatewhich is obtainable by the process of the invention described above. Inaddition, the present invention relates to an orodispersible tabletwhich is obtainable by the process of the invention described above.

Hence, the present invention relates to an orodispersible tablet whichis preferably obtainable by the process of the invention, containing

-   45 to 70% by weight, preferably 50 to 60% by weight, sildenafil    base,-   10 to 35% by weight, preferably 20 to 30% by weight, wicking agent,    in particular microcrystalline cellulose,-   5 to 20% by weight, preferably 7 to 15% by weight disintegrant, in    particular crospovidone and/or starches or starch derivatives, in    particular sodium carboxymethyl starch,-   0 to 5% by weight, preferably 1 to 3% by weight, glidant, in    particular silicon dioxide,-   0 to 10% by weight, preferably 1 to 5% by weight, lubricant, in    particular sodium stearyl fumarate.

In a preferred embodiment of the orodispersible tablet of the invention,the ratio of volume in cm³ to mass of sildenafil base in mg is from 1 to5 cm³/mg, preferably 2 to 4 cm ³/mg.

Finally, a further subject matter of the present invention is the use ofsildenafil, in particular sildenafil base, in particulate form, whereinthe D50 value of the particle size distribution is 10 to 55 μm and theD90 value of the particle size distribution is 60 to 250 μm, for thepreparation of an orodispersible tablet with a hardness of 30 to 90 N,preferably 40 to 80 N, and a friability of less than 1%, preferably 0.01to 0.5%, particularly preferably 0.05 to 0.3%.

The present invention thus makes it possible to prepare anorodispersible tablet with an advantageously high sildenafil content,wherein the orodispersible tablet can be free of saccharide. Despite thehigh sildenafil content, the tablet of the invention produces anadvantageous feeling in the patient's mouth. The invention furtherprovides a technically advantageous (e.g. inexpensive) productionprocess which, especially also in the case of larger batches, leads toan advantageous content uniformity in the resulting tablets.

The invention will now be illustrated with reference to the followingexamples.

EXAMPLES

Preparation

The following production process was used to prepare orodispersibletablets according to Examples 1 to 3.

Substances 1 to 4 were sieved using a 1 mm sieve and filled into a steeldrum. Using a Rhoenrad asymmetric moved mixer, the substances were mixedfor 10 minutes. After that, the mixture was granulated with a drycompactor (Gerteis Polygran®). Substances 5 to 10 were sieved using a 1mm sieve. Substances 5 to 8 were mixed with the granules.

The mixture obtained in this way was then mixed for 10 minutes using anasymmetric moved mixer. Talcum and colloidal silicon dioxide were addedand mixed for 5 minutes. The glidant sodium stearyl fumarate was thensieved in, using a 0.8 mm sieve. After the glidant had been added to themixture, the mixture obtained was mixed for 2 minutes. The mixture readyfor tableting was compressed into tablets using different compressionpressures (Ex. 1: 0.025 kN/mm, Ex. 2a: 0.045 kN/mm, Ex. 2b: 0.02 kN/mm,Ex. 3: 0.02 kN/mm) with a rotary press.

Example 1

TABLE 1 Composition for the preparation of an orodispersible tabletcontaining sildenafil base 100 mg Starch 100 mg Name (mg/dose) % Innerphase: 1 sildenafil base 100.00 55.87 2 cellulose, microcrystalline40.00 22.35 PH 112 3 crospovidone 6.00 3.35 4 colloidal silicon dioxide2.00 1.12 Outer phase: 5 cellulose, microcrystalline 9.60 5.36 PH 112 6crospovidone 9.00 5.03 7 natural mint aroma 2.40 1.34 8 Aspartame ® 1.000.56 9 talcum 2.00 1.12 10 colloidal silicon dioxide 2.00 1.12 11 sodiumstearyl fumarate 5.00 2.79 Total: 179.0 100.0

Examples 2a and 2b

TABLE 2 Composition for the preparation of an orodispersible tabletcontaining sildenafil base 50/100 mg Starch 50 mg 100 mg Name (mg/dose)(mg/dose) % Inner phase: 1 sildenafil base 50.00 100.00 54.95 2cellulose, microcrystalline 19.00 38.00 20.88 PH 112 3 crospovidone 4.008.00 4.40 4 colloidal silicon dioxide 1.00 2.00 1.10 Outer phase: 5cellulose, microcrystalline 5.40 10.80 5.93 PH 112 6 crospovidone 4.509.00 4.95 7 natural mint aroma 1.50 3.00 1.65 8 Aspartame ® 0.60 1.200.66 9 talcum 1.00 2.00 1.10 10 colloidal silicon dioxide 1.00 2.00 1.1011 sodium stearyl fumarate 3.00 6.00 3.30 Total: 91.0 182.0 100.0

Example 3

TABLE 3 Composition for the preparation of an orodispersible tabletcontaining sildenafil base 100 mg Starch 100 mg Name (mg/dose) Innerphase: 1 sildenafil base 100.00 2 cellulose, microcrystalline PH 11240.00 3 crospovidone 6.00 4 colloidal silicon dioxide 2.00 Outer phase:5 cellulose, microcrystalline PH 112 10.80 6 crospovidone 9.00 7 naturalmint aroma 3.00 8 Aspartame ® 1.20 9 talcum 2.00 10 colloidal silicondioxide 2.00 11 sodium stearyl fumarate 8.00 Total 184.0

Examples 4a and 4b

In order to prepare orodispersible tablets in accordance with Example 4,substances 1 to 5 were sieved using a 1 mm sieve and filled into a steeldrum. Using a Rhoenrad asymmetric moved mixer, the substances were mixedfor 10 minutes. After that, the mixture was granulated with a drycompactor (Gerteis Polygran). Substances 6 to 11 were sieved using a 1mm sieve and added to the granules. The mixture obtained in this way wasthen mixed for 10 minutes using an asymmetric moved mixer. Talcum (12)and colloidal silicon dioxide (13) were added and mixed for 5 minutes.The glidant sodium stearyl fumarate (14) was then sieved in, using a 0.8mm sieve. After the glidant had been added to the mixture, the mixtureobtained was mixed for 2 minutes. The mixture ready for tableting wascompressed into tablets using different compression pressures (Ex. 4a:0.02 kN/mm, Ex. 4b: 0.03 kN/mm) with a rotary press.

TABLE 4 Composition for the preparation of an orodispersible tabletcontaining sildenafil base 50/100 mg Starch 50 mg 100 mg Name (mg/dose)(mg/dose) Dry granules: 1 sildenafil base 50.00 100.00 2microcrystalline cellulose 30.00 60.00 3 dibasic calcium phosphate 16.0032.00 4 sodium starch glycolate 2.00 4.00 5 colloidal silicon dioxide1.00 2.00 Outer phase: 6 sodium starch glycolate 3.00 6.00 7 starch15.65 31.30 8 natural mint aroma 0.30 0.60 9 menthol aroma 0.45 0.90 10lemon aroma 1.20 2.40 11 saccharine 0.10 0.20 12 talcum 1.00 2.00 13colloidal silicon oxide 2.00 4.00 14 sodium stearyl fumarate 3.75 7.50

Evaluation:

In Examples 1 to 3, it was possible to achieve concentrations of activeagent of more than 50% by weight, based on the total weight of theorodispersible tablet. Even with an amount of active agent of 100 mg,the total weight of the orodispersible tablet was well under 200 mg.

Friability

The friability for orodispersible tablets according to Example 1 was0.25%. The friability for orodispersible tablets according to Example 2with the 50 mg strength of active agent (Ex. 2a) was 0.05% and fororodispersible tablets with the 100 mg strength of active agent (Ex. 2b)it was 0.15%. Orodispersible tablets according to Example 3 exhibited afriability of 0.25%.

Hardness:

The average hardness for orodispersible tablets according to Example 1was 70 N. The average hardness for orodispersible tablets according toExample 2 with the 50 mg strength of active agent (Example 2a) was 50 Nand for orodispersible tablets with the 100 mg strength of active agent(Example 2b) it was 80 N. In addition, the average hardness fororodispersible tablets according to Example 3 was 70 N.

Disintegration Time

The average disintegration times were determined here immediately afterthe orodispersible tablets had been produced (time T₀.), after theorodispersible tablets had been stored for 7 days (time T₇) and afterthey had been stored for 25 days (time T₂₅) at 25° C. and 55% relativehumidity.

Time T₀

The average disintegration time for the orodispersible tablets preparedin accordance with Example 1 at time T₀ was 20 sec. The averagedisintegration time for the orodispersible tablets prepared inaccordance with Example 2 with a strength of active agent of 50 mg attime T₀ was 10 sec, and that for the orodispersible tablets prepared inaccordance with Example 2 with a strength of active agent of 100 mg attime T₀ was 35 sec. In addition, the average disintegration time for theorodispersible tablets prepared in accordance with Example 3 at time T₀was 25 sec.

Times T₇ and T₂₅

It has been found that the average disintegration time of theorodispersible tablets of the invention did not undesirably increasesignificantly even after the relevant storage time.

Taste/Feeling in the Mouth

Since taste sensations and sensations associated with the feeling in themouth can vary from one individual to another, 5 test candidates wereused to test the taste and the feeling in the mouth, and the averagescores for taste and feeling in the mouth were determined immediatelyafter the orodispersible tablets prepared in accordance with Examples 1to 3 were taken. The test for taste and feeling in the mouth wasperformed 1 hour after the last meal. The test candidates were all maleand non-smokers. The test room was neutral in odour, the temperature was20° C. The stimulated sensations were assessed and the test candidateswere trained in accordance with DIN 10950.

The test candidates were able to score their sentiments with regard tothe feeling in the mouth on a scale from 1 to 3. The different scores of1 to 3 were defined as follows: (1) “good feeling in the mouth”, (2)“medium feeling in the mouth”, (3) “bad feeling in the mouth”. Withregard to the feeling in the mouth, the vast majority of the testcandidates awarded a score of “good feeling in the mouth” to theorodispersible tablets according to Examples 1 to 3.

1. A process for the preparation of an orodispersible tablet comprisingsildenafil base, the process comprising the steps of: (I) preparing anintermediate comprising the steps of (i) mixing of (a-i) sildenafilbase, (b-i) a wicking agent, (c-i) a disintegrant, and (d-i) optionallya glidant, (ii) compacting the mixture, and (iii) milling the compactedmixture, (II) mixing the intermediate with one or more furtherpharmaceutical additives; and (III) compressing the mixture of step (II)to form an orodispersible tablet.
 2. The process according to claim 1,wherein particular sildenafil base is used as component (a-i), whereinthe D50 value of the particle size distribution of the particulatesildenafil base is from about 3 to about 30 μm and the D90 value of theparticle size distribution of the particulate sildenafil base is fromabout 5 to about 50 μm.
 3. The process according to claim 1, wherein theratio of weight of component (a-i) to combined weight of components(b-i) and (c-i) is from about 5:1 to about 1:2.
 4. The process accordingto claim 1, wherein the weight ratio of components (b-i) to (c-i) isfrom about 10:1 to about 1:1.
 5. A process for the preparation of anorodispersible tablet comprising sildenafil base, wherein sildenafilbase is used in an amount of from about 45 to about 70 wt % based on thetotal weight of the orodispersible tablet.
 6. The process according toclaim 1, wherein (b-ii) a wicking agent, (c-ii) a disintegrant, (d-ii)optionally a glidant and (e-ii) optionally a lubricant are used aspharmaceutical additives in step (II).
 7. The process according to claim1, wherein the process is carried out in the absence of solvents.
 8. Theprocess according to claim 1, wherein microcrystalline cellulose is usedas the wicking agent (b-i) and/or (b-ii) and/or crospovidone and/orsodium carboxymethyl starch is used as the disintegrant (c-i) and/or(c-ii).
 9. The process according to claim 1, wherein the compactionforce in step (III) is from about 0.001 to about 0.2 kN/mm².
 10. Anorodispersible tablet prepared according to claim
 1. 11. Anorodispersible tablet comprising 45 to 70 wt % sildenafil base, 10 to 35wt % wicking agent, in particular microcrystalline cellulose, 5 to 20 wt% disintegrant, in particular crospovidone and/or sodium carboxymethylstarch, 0 to 5 wt % glidant, in particular silicon dioxide, 0 to 10 wt %lubricant, in particular sodium stearyl fumarate or magnesium stearate.12. The orodispersible tablet according to claim 11, wherein the ratioof the orodispersible tablet in cm³ to mass of sildenafil base in mg isfrom about 1 to about 5 cm³/mg.
 13. An orodispersible tablet accordingto claim 12 with a hardness of about 30 to about 90 N, with a friabilityof about 0.01 to about 0.5%.
 14. Use of sildenafil in particulate form,wherein the D50 value of the particle size distribution is from about 1to about 30 μm and the D90 value of the particle size distribution isfrom about 5 to about 80 μm, for the preparation of an orodispersibletablet, preferably for the preparation of an orodispersible tablet witha hardness of about 30 to about 90 N and a friability of about 0.01 toabout 0.5%.